Resurrection of type IIL supernova 2018ivc: Implications for a binary evolution sequence connecting hydrogen-rich and -poor progenitors

TL;DR

This study presents long-term ALMA observations of supernova 2018ivc, revealing a unique rebrightening in synchrotron emission that sheds light on the progenitor's mass-loss history and its connection to binary evolution of massive stars.

Contribution

It provides the first millimeter-wavelength observation of rebrightening in a type IIL supernova, linking progenitor mass-loss history to binary evolution pathways.

Findings

Rebrightening occurred ~1 year post-explosion in synchrotron emission.

Progenitor experienced very high mass-loss rate ~1500 years before explosion.

SN 2018ivc bridges hydrogen-rich and -poor supernova progenitors.

Abstract

Long-term observations of synchrotron emission from supernovae (SNe), covering more than a year after the explosion, provide a unique opportunity to study the poorly-understood evolution of massive stars in the final millennium of their lives via changes in the mass-loss rate. Here, we present a result of our long-term monitoring of a peculiar type IIL SN 2018ivc, using the Atacama Large Millimeter/submillimeter Array (ALMA). Following the initial decay, it showed unprecedented rebrightening starting at ~ a year after the explosion. This is one of the rare examples showing such rebrightening in the synchrotron emission, and the first case at millimeter wavelengths. We find it to be in the optically-thin regime unlike the optically-thick centimeter emission. As such, we can robustly reconstruct the distribution of the circumstellar matter (CSM) and thus the mass-loss history in the final ~1,000 years. We find that the progenitor of SN 2018ivc had experienced a very high mass-loss rate >~10^{-3} Msun/yr ~1,500 years before the explosion, which was followed by a moderately high mass-loss rate (>~10^{-4} Msun/yr) up until the explosion. From this behavior, we suggest SN 2018ivc represents an extreme version of a binary evolution toward SNe IIb, which bridges the hydrogen-poor SNe (toward SNe Ib/c, without a hydrogen envelope) and hydrogen-rich SNe (SNe IIP, with a massive envelope).